The invention relates to an underbody panelling part of a wheel axle in the region of a wheel arch of a motor vehicle, and to a subassembly having an underbody panelling part of said type.
Against the background of the discussion regarding the reduction of CO2 emissions of motor vehicles, measures for reducing fuel consumption play an ever greater role. These include, inter alia, the lowering of the air resistance of the vehicle. Whereas optimum solutions have long been sought in the case of vehicle body design, the reduction of the air resistance of the underbody of the vehicle has still not advanced very far. Here, however, there is major potential for improvement, because the underbody, after all, can account for approximately 20% of the overall air resistance.
In the region of the front axle with the steerable wheels, the particular challenge is to realize an underbody panelling which allows for the variable wheel position.
In this regard, DE 10 2010 018 779 A1 has proposed, generally, that a panelling part be held on the motor vehicle so as to be movable in a manner dependent on a pivoting movement of a link element.
It is an object of the invention to provide an underbody panelling part which can be easily arranged, in the region of a wheel axle, in the wheel arch, and which can realize an effective reduction in air resistance.
This is achieved according to the invention by way of an underbody panelling part of a wheel axle in the region of the wheel arch of a motor vehicle. The underbody panelling part has a main body, the covering surface of which is variable and which has a fastening structure for fixed connection to the vehicle body and/or a fastening structure for fixed connection to a transverse link of the vehicle. The covering surface can be varied as a result of a wheel steering deflection, such that the underbody panelling part can follow the steering movements of the steering wheel of the motor vehicle, and thus the gap dimensions between the underbody panelling part and the wheel or the wheel carrier can be optimally kept small. It is not necessary for the entire underbody panelling part to be arranged so as to be rotatable or pivotable. Instead, the variability of the main body of the underbody panelling part is utilized for reversible variation of its covering (and thus flow-guiding) surface, as viewed from below such that the required region of the underbody is covered or opened up by the underbody panelling part in a manner dependent on the wheel position.
The underbody panelling part is preferably firmly fixed both to the vehicle body, in particular to an inner side of the wheel arch, in sections, and firmly fixed to the transverse link at points. For example, an edge of the main body may be firmly screwed to the inner side of the wheel arch at least in sections.
Here, it is possible for a major part of the surface of the underbody panelling part to be left unchanged and for only a small section to be provided for being correspondingly varied with the wheel steering deflection.
The fixing may also offer the required opposing force for the reversible variation of the covering surface of the main body.
In a preferred embodiment, the main body is designed to be flexible, and preferably elastic to a certain extent, for the variation of the covering surface. It is contemplated for a preload to be built up in the direction of the wheel carrier.
For example, the main body may have at least one section which is laid in substantially parallel folds and which can be reversibly pulled apart transversely with respect to the folds. Here, the main body section may be designed in the form of a corrugated bellows with accordion-like folds. As material, use may be made, for example, of a suitable plastic or a suitable coated fabric.
The folds are preferably positioned such that they firstly ensure a low-resistance flow around them, and secondly, they impart the greatest possible flexural stiffness to the main body. The folds preferably run in a longitudinal direction of the vehicle. To improve stability, it is for example possible for the fold edges to be reinforced by longitudinal bars which have higher stiffness than the material stretched between them.
A variation of the surface can be easily realized here by way of a transverse force on the folded section of the main body, in the case of which the folds are pulled apart or pushed together transversely with respect to the longitudinal direction.
In a preferred embodiment, at least one transverse web which runs transversely with respect to the vehicle longitudinal axis and which is composed of an elastic material is provided in the panelling part. It is possible for, in each case, one section which is laid in folds to be provided in front of and behind the transverse web as viewed in the vehicle longitudinal direction.
The transverse web may be designed so as to permit a movement in all spatial directions in order to compensate a spring movement of the wheel carrier in the z direction, relative movements in the x and y directions resulting from the axle kinematics, and movements of the axle components resulting from the elastokinematics.
Along one longitudinal side of the main body, there is preferably provided at least one flexible strut which, in the installed state, faces toward a wheel carrier of the motor vehicle. The flexible strut can be used to realize a transmission of force and thus a deflection of the underbody panelling part by the wheel carrier, for example.
A particularly good adaptation can be achieved if the flexible strut has flexible longitudinal webs, which converge at one end, and multiple flexible transverse webs which run parallel and which extend between the longitudinal webs, transversely with respect thereto. In other words, it is advantageous for the flexible strut to be constructed such that it can utilize the so-called fin ray effect. In this case, owing to the connection of two elastic outer webs to multiple flexible transverse webs which run in parallel and which become shorter in the longitudinal direction of the component, the effect arises that, when a force acts in the region of the end at which the longitudinal webs are spaced further apart, the end at which the longitudinal webs converge on one another curves in the direction of the action of force, and not away from the latter.
It is preferable if, along the longitudinal side of the main body, there are provided flexible struts with convergent ends, wherein the ends are directed away from one another, or one continuous flexible strut with two opposite converging ends. In this way, the fin ray effect can be utilized in order, in the event of a transmission of force to a region in the middle of the underbody panelling part by way of a steering movement, to bring about a pivoting-out movement of the front or rear edge, respectively, of the main body in the direction of the wheel in order to close the gaps that form.
Optionally, the transverse web lies between two flexible struts, such that, as a result of the fastening to the transverse link, good force transmission to the flexible struts is possible.
The invention also relates to a subassembly having an underbody panelling part according to the invention. The panelling part is mechanically coupled to the wheel suspension of the vehicle, more precisely to a part of the wheel suspension that moves during a wheel steering deflection, such that the covering surface is varied as a result of a wheel steering deflection. In particular, the underbody panelling part is mechanically coupled to the wheel carrier. The covering surface of the underbody panelling part may be varied, for example, by way of contact with a wheel suspension part which moves during the wheel steering deflection.
The subassembly thus comprises the underbody panelling part, the mechanical coupling and at least the corresponding part of the wheel suspension.
The transverse web may be fastened to a transverse link of the vehicle.
For the transmission of the steering movement, it may be provided that, on a wheel carrier of the vehicle, there are provided two guide projections which face toward the panelling part and which each, during a steering movement to the right or to the left, come into contact with the underbody panelling part, in particular with the one or more flexible struts.
The underbody panelling part may also have the effect of at least partially sealing off the wheel arch region against the ingress or emergence of air flows.
If, in the case of wheel arches through which cooling air flows, it is necessary to ensure good ventilation of the wheel arch, the underbody panelling part may optionally, at its end directed toward the vehicle rear end, delimit an air duct which is oriented substantially horizontally. The air duct permits an outflow of air from the wheel arch in a substantially horizontally directed air stream without turbulence, which would increase the air resistance.
The optional air duct may be formed by a gap between the underbody panelling part and an adjacent vehicle body section, through which gap the air can flow in parallel along the underbody of the vehicle.
Through the provision of an underbody panelling part of this type, it is possible for a ram lip or a ram body normally provided in the region of the front of the vehicle to be decreased in size, or omitted entirely.
The overall geometry of the underbody panelling part may be adapted by a person skilled in the art to the geometry of the wheel arch region and the required free travel of the underbody panelling part in all arising operating situations and driving states.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.